SWODY1
SPC AC 050059
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0759 PM CDT SAT OCT 04 2008
VALID 050100Z - 051200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
UPPER AIR PATTERN EVOLUTION CONTINUES ON SYNOPTIC SCALE...WITH
HEIGHTS CONTINUING TO FALL ACROSS ROCKIES AND GREAT PLAINS AS
TROUGHING SHIFTS EWD AND AMPLIFIES ACROSS GREAT BASIN/4-CORNERS
REGIONS. STG SHORTWAVE TROUGH IS EMBEDDED IN ASSOCIATED CYCLONIC
FLOW OVER SERN CA AND SRN NV -- AS OF 00Z -- AND SHOULD DIG ESEWD
ACROSS CENTRAL/SRN AZ THROUGH REMAINDER PERIOD.
MEANWHILE...SOMEWHAT WEAKER SHORTWAVE TROUGH -- NOW EVIDENT IN
MOISTURE CHANNEL IMAGERY AND VWP DATA OVER ERN UT AND SERN ID --
SHOULD LIFT NEWD ACROSS WY OVERNIGHT. RESULTING TIGHTENING OF
HEIGHT GRADIENTS AND INCREASE IN FLOW ALOFT ACROSS CENTRAL/SRN
ROCKIES WILL MAINTAIN AND SLIGHTLY STRENGTHEN LEE-SIDE
TROUGHING...AS WELL AS SUPPORT STG LOW LEVEL WAA OVER LARGE SWATH OF
PLAINS STATES AND MID/UPPER MS VALLEY.
AT SFC...WARM FRONT PREVIOUSLY EVIDENT FROM WRN KS SEWD ACROSS OK TO
CENTRAL TX HAS BECOME DIFFUSE...MANIFEST MORE AS MOISTURE THAN
THERMAL BOUNDARY -- EFFECTIVE DRYLINE -- DURING DAYLIGHT HOURS.
WARM FRONT IS REFORMING FARTHER N ACROSS CENTRAL PLAINS AND LOWER MO
VALLEY REGION...AND SHOULD STRENGTHEN AND LIFT NWD ACROSS PORTIONS
NEB/MO OVERNIGHT.
OLDER...QUASISTATIONARY AND DIFFUSE BAROCLINIC ZONE IN LOW LEVELS
WILL CONTINUE TO SUPPORT GEN TSTM POTENTIAL OVER S FL...KEYS AND
ADJACENT WATERS. MEANWHILE...LOW LEVEL COLD FRONTAL ZONE ASSOCIATED
WITH WRN CONUS MID-UPPER TROUGHING WILL MOVE SLOWLY EWD ACROSS
CENTRAL/SRN ROCKIES AND NRN HIGH PLAINS...MERGING WITH LEE TROUGHING
OVER PORTIONS CENTRAL/NRN HIGH PLAINS BY AROUND 12Z.
...IA AND UPPER MS VALLEY REGION...
WIDELY SCATTERED TO SCATTERED TSTMS SHOULD DEVELOP OVER THIS REGION
LATE IN PERIOD -- PRIMARILY AFTER APPROXIMATELY 08Z -- AND
MOVE/DEVELOP ENEWD ACROSS UPPER MS VALLEY TOWARD SERN MN AND WI.
STG LOW LEVEL WAA REGIME WILL CONTRIBUTE TO DESTABILIZATION ABOVE
SFC AND DEVELOPMENT OF CONVECTIVE POTENTIAL...AS CONTINUING
ISENTROPIC LIFT PROCESS BEGINS TO BOOST INCREASINGLY HUMID PARCELS
TO LFC. UPSTREAM RAOB/TAMDAR DATA AND TIME SERIES OF RUC FCST
SOUNDINGS SUGGEST THAT SUFFICIENT ELEVATED MUCAPE WILL DEVELOP TO
SUPPORT TSTMS -- 100-400 J/KG -- BUT ALSO...RELATIVELY HIGH BASED
AND WITH WEAK MOISTURE. GIVEN SUCH MEAGER BUOYANCY...AND EFFECTIVE
SHEAR MAGNITUDES AOB 35 KT IN MOST FCST SOUNDINGS...PRIND
ACCOMPANYING HAIL POTENTIAL IS TOO MRGL/CONDITIONAL TO CONTINUE
5-PERCENT PROBABILITIES.
...HIGH PLAINS WWD THROUGH INTERMOUNTAIN REGION...
GREATEST CONCENTRATIONS OF CONVECTION MAY REMAIN BENEATH AND JUST
AHEAD OF PROGRESSIVE CA/NV TROUGH...AND IN SRN HIGH PLAINS WAA
REGIME. AT LEAST MRGL MOISTURE...COOLING ALOFT AND RELATED
STEEPENING OF LOW-MIDLEVEL LAPSE RATES SHOULD OFFSET SFC COOLING
ENOUGH TO MAINTAIN THUNDER THREAT FROM CURRENT SRN NV CONCENTRATION
EWD AND SEWD ACROSS SRN UT/NRN AZ...PRIMARILY N OF UPPER JET AND
BENEATH ITS LEFT EXIT REGION. LOW LEVEL MOISTENING AND WAA WILL
SUPPORT CONTINUED THUNDER POTENTIAL OVER SRN HIGH PLAINS...BUT WITH
CAPE SUBSTANTIALLY LIMITED BY WEAK LAPSE RATES ALOFT. PRESENCE OF
STG DEEP-LAYER SHEAR IN BOTH AREAS INDICATES NONZERO SVR
THREAT...HOWEVER IT APPEARS TOO CONDITIONAL AND WEAK FOR AOA
5-PERCENT GRIDPOINT PROBABILITIES ATTM.
OTHERWISE...COMBINATION OF VERY MRGL MOISTURE AND POCKETS OF
ENHANCED MIDLEVEL DESTABILIZATION AHEAD OF SHORTWAVE TROUGHS WILL
SUPPORT EPISODIC...NON-SVR TSTMS ACROSS BROAD SWATH OF W-CENTRAL
CONUS.
..EDWARDS.. 10/05/2008
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